A few such tools already exist, though they are only compatible with the japanese version. By now, I've figured out how most of them work and I've had some fun using the different editing features. Still, I wish someone would make an editor that accepts the english version of this game!
Anybody interested to look into this? I can link to the original editor set if it's of any help to translate known data locations (I'm completely clueless in that regard). Thanks in advance for any contribution to make this real.